Conventionally, this type of an induction heating cooking device has had springs installed on components inside a main body, and has had a heating coil unit pressed against a top plate with the springs so that a distance between the heating coil and the top plate has been held (see Patent Literature 1 and Patent Literature 2, for example).
FIG. 23 shows a side sectional view of a conventional induction heating cooking device described in Patent Literature 1 and Patent Literature 2. As shown in FIG. 23, the conventional induction heating cooking device is configured by a box body consisting of a top plate 101 on which a cooking container as an object to be heated is placed, a frame 102 that covers side surfaces and an upper surface of outer peripheral edges of the top plate 101, and a framework 103 that configures side surfaces and a bottom surface of a main body as the induction heating cooking device. Inside the box body, a plurality of circuit substrates 104 that configure a drive control circuit for supplying a high-frequency current to a heating coil 109 are individually installed on substrate bases 105. The substrate bases 105 are placed in superposition on and fixed to the bottom surface of the framework 103.
A substrate base cover 106 is provided on the upper part of the circuit substrates 104. Springs 107 are placed on the substrate base cover 106, and the springs 107 support a coil base 108 by biasing the coil base 108 upward from below. The heating coil 109 is placed on the coil base 108. A vibration-proof rubber 110 is disposed on the coil base 108, near the outer peripheral part of the heating coil 109. When the springs 107 have pressed the coil base 108 upward, the upper surfaces of the vibration-proof rubbers 110 are brought into contact with the rear surface of the top plate 101, and a distance between the heating coil 109 and the top plate 101 is held at a constant distance. Ring-shaped ribs 111 for positioning are provided at the outer periphery of a portion of the coil base 108 that receives the springs 107, and the upper parts of the springs 107 fit inner sides of the ribs 111. A casing 114 is placed on and fixed to the bottom surface of the framework 103, while covering a blade 113 that is installed on a motor 112 and holding the motor 112. Then, the main body is disposed in the kitchen in such a way as to be hung on a top board 115 of the kitchen with a flange 103a of an upper part of the framework 103 and with the frame 102.
In the conventional induction heating cooking device configured as described above, components are stacked on the bottom surface of the framework 103, and the heating coil 109 is further paced on the upper parts of these components. Therefore, there occurs a phenomenon that the bottom surface of the framework 103 is deflected to a lower direction by load. Accordingly, when the heating coil 109 is fixed to the substrate base cover 106 without biasing upward the coil base 108 on which the heating coil 109 is placed, it has not been possible to keep constant a distance between the heating coil 109 and the top plate 101.
Consequently, in the configuration shown in FIG. 23, the top plate 101 is mounted on the framework 103, by providing the springs 107 between the coil base 108 and the substrate base cover 106. By providing the configuration in this way, the lower surface of the top plate 101 is brought into contact with the upper surfaces of the vibration-proof rubbers 110, and the coil base 108 is pressed down to a lower direction, so that the springs 107 become in a compressed state. As a result, a constant distance can be maintained between the heating coil 109 that is placed on the coil base 108 and the top plate 101. Therefore, the springs 107 in the induction heating cooking device are always in a compressed state. Further, by providing on the coil base 108 the ribs 111 to which the upper parts of the springs 107 fit, the coil base 108 is prevented from being deviated to a horizontal direction.
In the conventional induction heating cooking device configured as described above, load of many components including the heating coil unit inside the main body is always applied to the bottom surface of the framework 103. Therefore, after passing a long period, the bottom surface of the framework 103 has a possibility of being further deformed. However, the conventional induction heating cooking device is configured to have the springs 107 provided between the coil base 108 and the substrate base cover 106 so that the springs 107 press the vibration-proof rubbers 110 that are installed on the coil base 108 to the rear surface of the top plate 101. Therefore, a constant distance between the heating coil 109 and the top plate 101 can be secured without a change in the distance.
According to the induction heating cooking device, when the distance between the cooking container as an object to be heated that is placed on the top plate 101 and the heating coil 109 has changed, a high-frequency voltage and a high-frequency current that are generated in the inverter circuit which supplies the high-frequency current to the heating coil 109 change. As a result, product performance based on the design cannot be obtained. Therefore, maintaining the distance between the cooking container and the heating coil 109 without changing the distance is an extremely important subject in keeping the performance of the induction heating cooking device.